The administration of medicaments by inhalation is well known. Such medicaments are often administered in the form of solid powders. Pressurised metered dose inhalers (MDIs) are one well-known form of administration, but concerns about the environmental effects of the propellants used in such systems have lead to increased attention on so-called dry powder inhalers (DPIs). In such inhalers, a dose of powdered medicament is entrained in a swirling airflow and inhaled, the swirling airflow normally being created by the act of inhalation.
Many DPIs are configured for repeated use, ie for the administration of repeated doses of medicament to a patient. However, for many applications it may be preferable or more convenient for a DPI device to be used only once, for the administration of a single dose of a medicament (or a combination of medicaments), and then to be discarded. In addition to the requirements common to all DPI devices, such as the requirement for the device to deliver the medicament in a form that can reach the intended site of action (eg that a high proportion of the medicament can penetrate deep into the lung, where the medicament is for the treatment of a respiratory condition such as asthma), for disposable devices it is also important that all the medicament should be delivered to the patient, and little or no residue of medicament should remain in the device. Otherwise, disposal of the device could lead to contamination of the environment and the risk that the devices could be subject to abuse. Such a risk may be particularly pertinent in the case of a device that has been used for the administration of a highly potent and/or addictive medicament, or one that is dangerous when not properly used.
U.S. Pat. No. 5,152,284 discloses a disposable inhaler that contains a pre-pierced capsule. The capsule is captivated within an inhaler body formed from at least two parts, and holes in the capsule are closed by a cup that fits around one end of the capsule. The cap can be slid away from the capsule to open the holes. Air can then be drawn through the inhaler body and medicament in the capsule is drawn out through the holes and entrained in the airflow. Such an inhaler suffers from the disadvantage of relative complexity of manufacture, arising from the fact that the inhaler body has to be assembled around the capsule. Also, and particularly importantly, because the holes in the capsule are closed by the slidable cup, they are necessarily located at the end of the capsule that is distal to the mouthpiece. As a result, emptying of the capsule may not be as effective as would be desired, which may result in underdosing and also potentially dangerous medicament residues being discarded with the used inhaler. Also, exhalation through the device would have the effect of dispersing medicament into the surrounding atmosphere.
Another form of inhaler is disclosed in WO-A-03/75988. That document describes an inhaler in which a pre-filled container of medicament is displaced from a first position, in which the container is sealed, to an operative position, in which the container is held stationary within an airway. Certain embodiments of the inhaler are intended to be disposable. In all disclosed embodiments, the medicament container is introduced into a chamber that is considerably larger than the container and the container is immobile within that chamber. It is mentioned that movement of a medicament container, as occurs in other forms of inhaler, eg those disclosed in WO-A-98/26828, may be undesirable as it may be audible.